This is one of the most common causes of shoulder pain, associated with irritation or damage to the tendons that stabilize the shoulder. The pain usually worsens when moving the arm, raising it overhead, performing repetitive movements, or lying on the affected shoulder. Causes include chronic overuse, trauma, degenerative changes, or shoulder impingement syndrome. If left untreated, this condition can limit shoulder movement, interfere with daily activities, and lead to weakness in the arm muscles. Treatment depends on the severity of symptoms and the nature of the injury—it may include medication, physical therapy, and, in some cases, interventional procedures or surgery.